The present invention relates to a reactor for carrying out an exothermic process, such as a Fischer-Tropsch process. It especially relates to a fixed bed reactor comprising a gas distribution system in the bottom of the reactor. In a preferred embodiment the reactor comprises highly porous catalysts. The invention further relates to the use of the reactor.
As is explained in WO 2005/075065, Fischer-Tropsch processes are often used for the conversion of gaseous hydrocarbon feed stocks into liquid and/or solid hydrocarbons. The feed stock, e.g. natural gas, associated gas, coal-bed methane, residual (crude) oil fractions, coal and/or biomass is converted in a first step to a mixture of hydrogen and carbon monoxide, also known as synthesis gas or syngas. The synthesis gas is then converted in a second step over a suitable catalyst at elevated temperature and pressure into paraffinic compounds ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, more.
Numerous types of reactor systems have been developed for carrying out the Fischer-Tropsch reaction. Fischer-Tropsch reactor systems include fixed bed reactors, in particular multi-tubular fixed bed reactors, fluidized bed reactors, such as entrained fluidized bed reactors and fixed fluidized bed reactors, and slurry bed reactors, such as three-phase slurry bubble columns and ebullated bed reactors.
The Fischer-Tropsch reaction is highly exothermic and temperature sensitive and thus requires careful temperature control to maintain optimum operating conditions and hydrocarbon product selectivity.
Commercial Fischer Tropsch fixed-bed and three-phase slurry reactors typically utilize boiling water to remove reaction heat. In fixed-bed reactors, individual reactor tubes are located within a shell containing water/steam typically fed to the reactor via flanges in the shell wall. The reaction heat raises the temperature of the catalyst bed within each tube. This thermal energy is transferred to the tube wall forcing the surrounding water to boil. In the slurry design, cooling tubes are placed within the slurry volume and heat is transferred from the liquid continuous matrix to the tube walls. The production of steam within the tubes provides cooling.